In recent years, a display device including a touch panel in which a display screen is touched by a finger of a user, a pen, or the like to input information has been used for mobile electronic equipment such as a mobile phone and a smartphone. Known examples of such a touch panel are a resistive touch panel in which changes of a resistance value at a touched part are detected, a capacitive touch panel in which changes in capacitance are detected, and an optical sensor touch panel in which changes of the amount of light are detected.
The capacitive touch panel is provided with driving electrodes for application of driving signals and detection electrodes intersecting with the driving electrodes and for detection of the signals. The driving signals are input to the driving electrodes while the driving electrodes are sequentially scanned, and capacitance between each driving electrode and each detection electrode is detected by a touch detection unit. In a case where an external object such as a finger contacts a surface of the touch panel, capacitance of each detection electrode changes. The touch detection unit detects the changed capacitance, and input coordinates are calculated based on a signal of the capacitance change detected in each detection electrode. For example, Japanese Patent Application Laid-Open Publication No. 2013-222421 (referred to as Patent Document 1, hereinafter) describes a liquid crystal display device with a capacitive touch detection function.